Swinging crane with high mechanical advantage braking



United States Patent [72] Inventors William J. Lado Rome, and

John F. Hefferin, Port Washington, New York -69; 74/425; 192/4; 254/170; 188/(C0nsulted) [56] References Cited UNITED STATES PATENTS 2,017,083 10/1935 Willink 192/4 2,091,225 8/1937 Eaton 254/170 2,250,586 7/1941 Lamond 192/4 2,428,163 9/1947 Hubbard 212/69 2,557,958 6/1951 Fitzsimmons.. 192/4 3,298,462 l/1967 Morris 254/184 FOREIGN PATENTS 105,647 2/1927 Germany 212/69 1 Primary Examiner- Harvey C. Hornsby Att0rney Darbo, Robertson and Vandenburgh ABSTRACT: Smooth and safely adequate braking for a swinging boom of a crane is provided by a disc brake geared to the rotating structure with high mechanical advantage including a worm gear slightly too low in ratio, and too high in thread lead angle, to be self-locking. The disc brake is hydraulic, applied by foot-controlled master cylinder. The hydraulicbrake can be locked in braking condition hydraulically by a tight-closing valve actuated manually.

v W; .25 F 24- 51. 1,1 1 1:" 2 i: Z15 g" I 1' 4'1 II I I 4 1'2 Patented N av. 10, 1970 ore Sheet BACKGROUNDOF THE INVENTION The invention. of which public dissemination .iS Offered in the event that a patent issues thereon, relates to anirnproved apparatus for smoothly and reliably slowingand stopping the slewing action of aswinging crane. In recent yearsthe advent of longer teleSS OPic boomsand the development of swinging cranes with higher tonnage capacities have been accompanied by increasingly greater pealt angular momentum of. the swiriging crane, Hence, the problemofbraking-theslewing motion,

[,e. swinging side-toj si de, is becoming more and more severe. in spite of extremely high angular momentum the braking must be smooth and} safely adequate. it will be appreciated that their smopthriessof the braking action is particularly irin portant inpre'vent'ing'the' hanging load from becoming a swingingpenduium.

sum-nay GETREINVENTION Smooth and safely adequate braking for a swinging boom of aeran is providedby abralte geared to the"- rotating structure with high mecha atadvai t 8%- The gearinglemployed in ac cordance with this invention ptovidesia gear ratiobetween about 83 to landBiOft'o 1 preferably in? the neighborhood of 1-5- to l between the input andout'put o'f thebraking mechanism, and the drive gearing mechanisrna It is essential however that the mechanical advantage not be high enough -to provide self locking and that" the crane-{turntable beicapable-of smooth coastirig; In a preferred embodiment oil-this invention, the gearing by w-hich the brake isgeared to tli'erotatingi structure is the same mechanism by which the; rotating structure is driven. l-leret'ofore, the: driving mechanisms have, generally employed gear ratiossufficientlyihigh to be self-locking, e.gr 40'to l' and higher. Such?rnechanisrr scould be'operated only bela driving force'appliedto one end ie, motori end', of thegear train'sThis was especiallyrtrue-when worm-gears having highgear ratio-and relatively shallowlead angles constituted part of the drivingsmechanism t- Hence,,whi l e the turntable could be smoothly turnedbythe actionof adrivingmotOr through the gear train, the gear train could-not be'rotated as a result of forcesap pliedto the-geartrain-bythe-turntable. Cohsequently, in such-systems the turntable could not coast because of the self-locking. characteristics of the turntable driving mechanismyor ifth'ey,c'o,uld coast at all; due to momentum at the high-speed end of the gcaring, the coasting was much too-limited for present needsiiHence, assoon as the operation of the 'driving-imo'tor ceased the turntable-tended to jerk to a stop because of the self-locking characteristics.

f l DESIGNATIONOFFlGURES'OFTHBDRAWlNGS FIG. 1 is a perspective viewofatruck borneswingingcranehaving. a 'telescop'ic boom, WilhiWhiCh this inventionish'ighly advantageous F I042 is a vertical crossssectional viewtalten approximatelyalong the line-ZfZI inFlGr 3;il lustrating: key elements of this" inve rition."

FIG. 3 isra fragmentary; perspective view showing relative positions of keyrfeature's of this invention;

F-lG. 4 is a schematicdiagramfillustrating5ahydraulic bralcserninationinreturn for the' grantofa patent,- is detailed to en-1 sure adequacyj and aidunderstandihythis is notl'intended to prejudicethat purpose jof a 'patent-whichis 'tocover' each new inventive: conceptiltherein no' matter how others may later disguise it. by variationsin;form: or;iadditions orfurther improvements. Th ejclaims atthe-end hereof areintended as the chief aid toward this purpose; as it =is-;these that meet the "that the'brake disc 41; worm wheel gear 33, vertical shaft 30,

requirement of pointing out the parts, improvements. or combinations in which the inventive concepts are found.

' FIG. 1 illustrates a trucloborne crane having a turntable 11 mounted on a fixed base plate 12 which is supported by the truck chassis 13. The stationary gear 14 is part of the mechanism used for ro'tating'or slewing the turntable it. The

crane illustrated in FIG. 1 has a telescopic boom 15 which is shown in a somewhat contracted condition, supporting the load 16. The equipment used to raiseand lower or extend or contract the boom does not constitute part of the invention.

and hence will not be discussed further.

in FIG. 2 attachment of the gear 14 and the base plate l2to the chassis 13' is illustrated schematically by the inclusion of bolt means 18. Hence in FIG. 2 only parts secured by this bolt, namely the gear 14-, and the base plate 12 are fixed, that is, statiortary, with respect to the tr'ucl't chassis 13. The elements mounted on turntable l1 and turntable bearing means or race ring 21 move with thecrane boom whenever the boom 15 is in slewing rnotion. The bearing 22 schematically illustrates supporting means which provide both upward and downward support of the turntable bearing ring 21 while permitting the turntable bearing ring to rotate with the boom. Gear box 23 is fixed to turntable ll; Gear box 23 is closed by cover 24 and upper bearing support element 25'. The stepped drive shaft is mounted onsuitab'leflower bearings 31 and upper bearings 32'. Worm wheel gear 33is f xed to shaft 30 within gear box 23 and spur gear 35 is fixed to the shaft 30 near itslowermost end outside of the gear box- 23in such a positionithat the spur gear 35 meshes with stationary g'ear' 14. Worm wheel gear 33 meshes with'worm 35 fixed to shaft 40. The brake disc 41 is also fixed to shaft'40and is situated outside of the gear box 23. FIG. 3" further illustrates the spatial relationship between key elements" of this invention. The hydraulic motoris worm' wheel gear 33 (see FIG. 2) and with it vertical shaft 30 to which spur gear SS'isfixed'. The relative position of spur gear 35 is also illustratedin Fit]; 3 in which it is apparentthat spur gear 35' meshes with circular stationary gear 14. As the hydraulic motor 50 causes rotation of shaft 40, the result is pliedto and rcleasedfrom cylinders 57 is conveyed by hydrau-' lie brake line 58. i g

FlCr. 4 schematically illustrates a hydraulic braking system. The brake disc dl isfixed'to shaft 40 and therefore rotates with-shaft 40. The peripheral portion of the brake disc moves betweenopposing pressure elements 'lfhese'elementscttn generate friction along the-lateral orface surfaces 42 of brake.

disc 41 asa result of hydraulic pressure within brake cylinders 5-7. The brake cylinders 57 are in hydraulic communication with master cylinder by means of brake line 58 and bran'ch brake lines 59. The tightly closing valve 61, e.g. a gate valve, locatedin hydraulic line 58 permits interruption of the hydraulic communication between brake cylinders 57 and master cylinder 60'.-The pistontnot shown) within the master cylinder-"60 is'drive'n by foot pedal 62.This' provides the pressure within the hydraulicsystemwhich results in the thrusting of friction elements 55' into friction contact with brakedisc 41; Upon release of pressure'on the pedal 62, resilient means (not shown).return the pedal to its nonbraking position, causing return of hydraulic fluid to the master cylinder 60 and release of thrust of elements 55. However, tight closing valve 61 is operated'manually by handle 63. Hence, while the hydraulic line 58 is under braking pressure closing of the valve 61 permits locking of the friction elements in their braking condition.

OPERATlON OF SLEWING BRAKE While turntable 11 is in slewing motion, i.e. rotational movement around its axis, spur gear 35, which is in mesh with stationary circular gear 14, rotates. This causes rotation of shaft 30 to which spur gear 35 is fixed and with it causes rotation of worm wheel gear 33 which is also attached to shaft 30. Rotation of the worm wheel 33 causes rotation of worm gear 35 and shaft 40 to which worm gear 35 is attached. As shaft 40 rotates, so also does brake disc 41 which is fixed to shaft 40. Hence, to slow down or stop the rotation of turntable 11 in accordance with the use of this invention, pressure is applied to foot pedal 62 thereby thrusting opposing friction elements 55 against the lateral surfaces 42 of brake disc 41. This opposes the rotation of shaft 40 and worm gear 35, and worm wheel gear 33. Hence, the rotation of shaft 30 is also opposed with the ultimate result that the rotation of gear 35 is smoothly retarded as a result of the braking forces applied to brake disc 41. As the rotation of spur gear 35 is smoothly slowed, so also is the rotation of turntable 11 around its axis since spur gear 35 meshes with stationary gear 14.

it will be appreciated that in accordance with this invention brake disc 41 is geared to the stationary element 14 with high mechanical advantage; also it is essential that the gearing therebctween be of sufficiently low ratio that the system does not become self-locking with respect to forces applied to it from spur gear 35. When in accordance with a preferred embodiment of this invention, which is specifically illustrated in the drawings; a worm gear is used in the gearing system, the lead angle of the worm gear must be sufficiently steep to permit the shaft 40 to be driven as a result of driving forces applied by the rotation or slewing motion of the turntable. Naturally, the exact range of usable lead angles on such a worm gear will depend on the particular dimensions of the elements coacting therewith, on the amount of lubrication provided, on the amount of vibration present, and other variables. We have found that worm gears having thread lead angles as low as 9 are eminently satisfactory for use in accordance with this invention. Worm gears having lead angles of or less do not provide a smooth coast, and hence their use is not in accordance with this invention. Use of a worm gear having 27' lead angle in accordance with a preferred embodiment of this invention permits the turntable to coast smoothly after the motor-derived driving forces terminate. This permits the application of braking forces on brake disc 41 while it is being driven by the momentum of the rotating turntable 11 and boom 15.

Hence, in accordance with this invention the braking forces applied at disc 41 have a high mechanical advantage with respect to the slowing of the slewing of the turntable. Thus, in accordance with this invention the slewing motion may be smoothly and precisely controlled.

It is commercially important (costwise) thought not in theory essential that the brake system of this invention be part of the turntable slewing-drive mechanism. It is essential that the turntable be free of attachment to any mechanism which is self-locking with respect to slewing motion of the turntable.

We claim:

1. In a rotatable crane having a stationary base structure with a boom and a turntable mounted thereon, said turntable being capable of coasting, slewing motion, said crane having drive gearing means for operatively connecting said rotatable turntable with said stationary base, the improvement comprising: a rotatable braking element operatively connected to said drive gearing means; nonrotative braking means operable by the operator and responsive in accordance with the force he exerts for opposing the rotation of the rotatable braking element but normally biased to a nonbreaking position; said drive gearing means having a gear ratio sufliciently high to provide high mechanical advantage, and below a self-locking ratio but sufficiently low to permit said braking element to be rotated as a result of the coasting slewing motion of the turntable.

2. An apparatus as in claim 1 in which said drive gearing means includes a worm gear having a thread lead angle greater than 9.

3. The apparatus of claim 1 in which said gearing includes a worm gear having a thread lead angle of about 1 1.

4. An improved slewing-motion control apparatus for use in a rotatable boom crane comprising a relatively large circular spur gear which constitutes part of the means for swinging the crane, the center of said gear being the axis of rotation of the crane; a small spur gear in mesh with the stationary gear; a control mechanism output shaft; a control mechanism input shaft; nonself-locking gearing connecting said output shaft and input shaft; a slewing-drive motor; and a brake disc; the small spur gear being fixed to the output shaft, the control mechanism input shaft being operatively connected to the slewing-drive motor and to said brake disc, said brake disc being operated by a hydraulic system which includes a master cylinder, a foot pedal operating said master cylinder, and a manually operated tightly closing valve for interrupting the hydraulic connection between the brake disc and the master cylinder, said gearing including a worm gear on said input shaft, said worm gear having a thread lead angle greater than 9, said gearing providing a gear ratio between the input shaft and output shaft of between 8 to l and 30 to 1, whereby the momentum of the coasting slewing-motion of the turntable and boom causes the small spur gear to rotate and with it the output shaft, the gearing, the control mechanism input. and brake disc to rotate; and means to apply friction forces to the brake disc to oppose rotation of the control mechanism input shaft, the gearing, the output shaft and the small spur gear, thereby smoothly and reliably controlling the rotation of the crane.

5. ln combination with a crane turntable for swinging a crane boom, a stationary ring gear, and a pinion meshing with the ring gear for turning the turntable, means fordriving the pinion including a worm wheel rotating with the pinion, a worm driving the worm wheel, and a motor turning the worm; a brake disc turning with the worm; and nonrotative hydraulic brake means, operable by the operator and responsive in accordance with the force he exerts for braking the disc, but normally biased in nonbraking position; said worm wheel and worm providing a high mechanical advantage in the range between 8 to l and 30 to 1, said worm having a sufficient lead angle to permit reliable smooth coasting when the brake disc and motor are free to turn under the influence ofthe momentum of the turntable and boom.

6. ln combination with a crane turntable for swinging a crane boom, a ring gear, and a pinion meshing with the ring gear for turning the turntable, means for driving the pinion including a worm wheel rotating with the pinion, a worm driving the worm wheel, and a motor turning the worm; a brake rotor turning with the worm; and nonrotative hydraulic brake means operable by the operator and responsive in accordance with the force he exerts, for braking the rotor but normally biased in a nonbraking position; said worm wheel and worm providing a high mechanical advantage in the range between 8 to l and 30 to l, and said worm having sufficient lead angle to permit reliable smooth coasting when the brake rotor and motor are free to turn under the influence of the momentum of the turntable and boom. 

